This invention relates to mining conveyor assemblies, and has been developed primarily in relation to the requirements which arise in underground mining wherein the main appartus is a machine for cutting or otherwise extracting the material to be mined, for example coal, travels along a face presented by said materials to such apparatus, and one or more cables are attached to this machine to convey services thereto.
The expression "cable" used herein is intended to denote any elongated flexible member primarily for conveying electric current, but includes also a flexible member for conveying fluid under pressure such as a flexible hose.
In mining, by the use of apparatus as above described, and in particular in coal mining by the method known as long wall coal mining, a conveyor assembly extends along and adjacent to the face, and the machine by which the coal or other mineral is extracted travels along a trackway afforded by the conveyor assembly with the cable or cables extending from such machine and lying generally alongside the conveyor assembly on the goaf side remote from the face. It is common practice to provide a carrier means on the conveyor assembly at the goaf side within which the cable or cables lie for the purpose of preventing the cable or cables taking up runs of random configuration which would interfere with the proper operation of the machine, become snagged around adjacent apparatus such as roof supports, and generally be exposed to damage resulting from such run or configuration.
In addition, it is an operational requirement that at each of a plurality of stations spaced apart along the face, the personnel engaged in the mining operation shall be able to transmit a signal to a main control station normally situated at one end of the face for the purpose of enabling an operator thereat to stop or start the conveyor assembly. It is a further requirement that the personnel shall be able to stop the operation of the conveyor assembly by operation of a control unit at each of the stations along the control face (independently of the facilities provided at each of these stations for signalling the operator at the main control station).
Control units of the kind to give effect to these requirements (herein referred to as "control units of the kind specified") normally include a signalling switch (usually a push-button operated switch spring-loaded to an off position) and a further switch, normally termed a lock-out switch, which can be moved from its normal unoperated position to an operated position in which it is held by retaining means independently of continued pressure or force exerted on the switch by the person operating it. The signalling switch conveys a signal to the operator at the main station to stop or start the conveyor (according to the nature of the signal given), and the lock-out switch produces stopping of the conveyor independently of any action on the part of the operator at the main station. Further, the control unit is usually provided with indicator means in the form of a lamp which is normally unenergised but which is energised and hence illuminated whenever the lock-out switch is moved from its unoperated to its operated position.
One form of conveyor assembly at present in service comprises a fence structure defining a trough open at its upper side, said trough providing the carrier means of the conveyor assembly. The inner side wall of this trough is formed by the upstanding goaf or spill plate of the conveyor assembly while its outer side may be formed by a series of longitudinally successive plates each having a length corresponding to a length of a section of the conveyor. The latter is normally formed of sections articulately connected to each other to allow the longitudinally successive sections of the conveyor assembly to be advanced one after another towards the face as the coal or mineral is extracted therefrom.
Each longitudinal plate is connected to the spill plate of the conveyor assembly by a base section of the trough, so that, in effect, the trough consists of a number of longitudinally successive sections.
At adjacent ends the outer side plates of the trough are in some cases connected to each other by flexible straps which admit of snakewise advancement of the conveyor assembly.
One of the disadvantages of this arrangement is, however, that despite the strip successive sections of the trough do afford gaps between adjacent ends of the outer side plates and the cables may become trapped in these and subject to damage.
The trough also frequently becomes filled by an accumulation of debris and coal, which interferes with proper movement of the cable or cables which it carries.
Further, the outer side plate of each individual trough section is rigidly connected to the spill plate of the conveyor assembly and thus cannot deflect in a vertical plane. It is sometimes the case that a portion of a cable will become trapped between the other side of the outer plate and some adjacent piece of apparatus such as a roof support, and the unyielding character of the outer side plate then leads to damage of the cable.
In yet another construction at present in service, the carrier means comprises a series of U-shaped brackets spanned at their upper ends by flaps which can be opened and closed to admit of entry and removal of the cable. The disadvantage of this arrangement is that again the brackets are rigid and consequently the cable can become trapped between the bracket and a roof support advancing towards this with resultant damage to the cable.
Furthermore, it is necessary for an operator to lift the flaps to allow the cable to pass into and out of the aperture afforded by the bracket each time the cutting or extracting machine passes.
Additionally, whilst the cable or cables associated with the mining machine are "movable" to the extent that loop-like runs of these cables lie in the trough afforded by the cable carrier means with such loops occupying a proportion of the length of the trough dependent upon the position of the mining machine, there are also other cables (herein called static cables) which form part of the control and/or indicator system for controlling operation of the main apparatus (in this case the conveyor). These static cables normally lie on the goaf side of the trough in which the "movable" cables are accommodated and certain of the static cables, as appropriate, are connected to the control units which are situated at stations spaced apart along the face as previously mentioned.
In addition, from the point of view of mounting the control units of the kind specified which form part of the control and/or indicator system associated with the conveyor at a position at which the personnel present in the mine working can have rapid and convenient access to these control units the most suitable place for mounting these control units is on the outer wall of the conveyor.
However, this creates a number of additional problems certain of which are concerned with the "movable" and "static" cables and certain of which are concerned with the approach of mine roof supports to the conveyor.
If the control units are mounted at the inner side of the outer wall of the trough so as to lie within the trough itself, they obstruct movement of the movable "cables" in the trough as the mining machine travels along the conveyor. If the units are mounted at the outer side of the outer wall of the trough they do cause some obstruction to the installation of the static cables supported in a channel at the outer side of this wall of the trough by virtue of overhanging the mouth of this channel, but more importantly the control units themselves are then necessarily placed in close proximity to the forward ends of movable roof supports which have to be brought up close to the conveyor so that the roof supporting superstructure of these supports can extend over the conveyor as close as possible to the face of the mine working. In this respect it is a requirement that between the face side of the conveyor on the face of the mine working a "prop-free front" should be maintained to allow unobstructed progress of the mining machine and this in turn requires that the foremost props of each support could be brought close as possible to the outer or goaf side of the conveyor.
Even if the props are arrested at a position in which they are short of the control units, the space between the control units and the props is comparatively small making it difficult for mining personnel to move along the conveyor between this and the roof supports, but also there is a considerable risk that the props will come into contact with the control units especially where the floor of the mine working presents a slope either laterally along the coal face or towards the coal face.